Discussion
Ischemic necrosis of the tongue has occasionally been reported, and is mainly associated with GCA [
2]. GCA, or temporal arteritis, is a systemic granulomatous arteritis that involves medium and large arteries, especially branches from the aortic arch, and is mainly found in older women [
3]. The cause of this disease is unknown, although it may be an immune-mediated condition [
4]. The clinical manifestations of GCA include headache, ocular symptoms, masseteric pain, and tongue pain [
3], and systemic corticosteroid therapy is known to be effective for ameliorating the symptoms of GCA. Lingual arteritis can develop in 25 of the patients with GCA, and 15 % of these patients experience lingual artery infarction [
4]. In cases of GCA, tongue necrosis may develop secondary to the lingual arteritis, and is typically unilateral, with the exception of one reported case of bilateral tongue necrosis [
1,
5]. The diagnosis of GCA usually depends on a clinical suspicion, and arterial biopsy can be performed for unclear cases. The laboratory findings in cases of GCA may include an elevated erythrocyte sedimentation rate, elevated plasma fibrinogen levels, and elevated α-2 globulin levels [
4]. Other known causes of tongue necrosis include Kawasaki disease, Wegener’s granulomatosis, DIC, and essential thrombocytosis, although these cases are rarely reported [
1].
Tongue necrosis was first reported as a sequela of shock in 2007 [
2]. The same group also reported a case series of tongue necrosis that was associated with cardiogenic shock in 2010 [
1], and they suggested that impaired perfusion of the tongue in cases of severe shock appeared to be the most reasonable explanation. However, relative blood flow to the heart increases during circulatory shock, and brain perfusion is maintained. Furthermore, the tongue is well supplied by the bilateral lingual arteries and branches of the facial and pharyngeal arteries. Therefore, it is difficult to explain how decreased blood flow to the tongue could occur without concomitant hypoperfusion of the gut, skin, and musculoskeletal system. However, Roman et al. have presented a hypothesis that could explain the hypoperfusion of the tongue during severe shock: blood flow to the internal carotid artery might be protected at the expense of the external carotid system during periods of decreased circulatory volume, and this would reduce the supply of blood to the tongue, which is a potentially susceptible muscular end organ [
1].
A search of the literature reveals several other potential causes of tongue necrosis, such as the prolonged use of terlipressin (an anti-diuretic hormone analogue) [
6] and DIC [
7]. However, it remains unclear what severity of DIC, or what dose of vasopressor treatment, can cause tongue necrosis. As shown in Table
1, the two patients in this report experienced different clinical courses. Patient 1 responded to the critical care with a short period of circulatory shock, and the delivered dose of the vasopressor seemed to be adequate. In contrast, Patient 2 experienced postoperative refractory shock, which necessitated high-dose vasopressor treatment to maintain adequate tissue perfusion. Moreover, Patient 1 did not exhibit any concomitant signs of hypoperfusion to other organs. Therefore, we cautiously suggest that there might be no specific vasopressor dose or severity of shock that must be exceeded to cause ischemic necrosis of the tongue. If the hypothesis that vasopressor or circulatory shock might cause tongue necrosis is correct, other contributing factors are likely needed to induce ischemic necrosis of the tongue during shock. Our cases, and the other reported cases [
1], exhibited bilateral tongue necrosis with rapid progression, and the necrosis progressed from the distal section to the proximal section of the tongue, which was less consistent with local pressure from an endotracheal tube and more consistent with a systemic process. This feature was also different from the unilateral necrosis that is observed in cases of GCA, which is a slowly progressing immune disease. Thus, it is possible that no single factor can cause bilateral lingual artery infarction in patients with circulatory shock, and the tongue necrosis may be promoted by complex interactions between the decreased circulatory volume, DIC, vasoconstrictor use, and pressure on the tongue from the endotracheal tube. Therefore, we suggest that tongue necrosis might be induced by any severity of shock, and at any time during the shock treatment, if the interaction(s) between these contributing factors is triggered. Moreover, ischemic necrosis of the tongue might predict a poor prognosis, despite apparent improvements in the other manifestations of shock.
We noticed that our patients developed septic shock secondary to gangrenous necrosis of the intestine. According to the intraoperative findings, Patient 1 seemed to have developed nonocclusive mesenteric ischemia, because we observed no occlusion of the major mesenteric vessels or other causes of ischemic enteritis. This disease entity is considered the end result of the physiological response to a decreased intravascular volume, and the splanchnic vasoconstriction can exhibit a profound and early onset, even before systemic hemodynamic instability arises [
8,
9]. Therefore, undetected circulatory compromise in Patient 1 might have proceeded before the gangrenous necrosis of the intestine and septic shock eventually occurred. We hypothesize that the lingual artery infarction might have already developed and that critical end-organ damage at the tongue had progressed, similar to the pathogenesis of the nonocclusive mesenteric ischemia, despite the manifestations of septic shock improving after the operation. However, this hypothesis cannot be applied to Patient 2, because her intestinal necrosis seemed to be caused by mechanical herniation of the intestine.
Conclusion
In conclusion, we suggest that ischemic necrosis of the tongue is an under-reported manifestation of any type of circulatory shock. The condition may have a complex pathological mechanism, which might consist of interactions between several contributing factors, such as a decreased intravascular volume, DIC, vasopressor treatment, and mechanical pressure from the endotracheal tube. Furthermore, it is possible that no single factor can cause tongue necrosis. Therefore, clinicians should be aware of the possibility of ischemic necrosis of the tongue in patients with circulatory shock, even if they exhibit clinical improvement, as this awareness may facilitate estimation of their prognosis and preparation for clinical deterioration.